A flow-through gas cell and a method for passing a sample gas through a flow-through gas cell for spectroscopy are disclosed. In an embodiment, a flow-through gas cell is disclosed. The gas cell includes a substantially cylindrical interior cavity. The interior cavity comprises an inner surface that is reflective. In addition, the gas cell includes a gas inlet and a gas outlet. In the gas cell, a source is disposed on a side of the gas cell, and a detector is disposed on the same side of the gas cell as the source. The source emits electromagnetic radiation, and the detector detects electromagnetic radiation. The gas cell further includes mirrors disposed on opposing ends of the interior cavity.